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:desktop_computer: CSA Chapter 1.3 Understand I/O in Computer System, Need…
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- Acts as an interface with the CPU and memory via the system bus/ central switch.
- Acts as an interface with one or more peripheral devices by tailored data links.
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- CPU is tied up for the duration of the transfer while doing a relatively simple task
1. The processor initiates the DMA transfer by supplying the I/O device address, the operation to be performed, the memory address destination/source, the number of bytes to transfer
2. The I/O DMA controller manages the entire transfer (possibly thousand of bytes in length), arbitrating for the bus
3. When the DMA transfer is complete, the I/O controller interrupts the processor to let it know that the transfer is complete
- There may be multiple DMA devices in one system
i. Processor and I/O controllers contend for bus cycles and for memory
